pub fn prepare_admm_spectral(
local_field: &[f64],
grid: &Grid,
bdir: (f64, f64, f64),
rho: f64,
) -> (Fft3dWorkspace, Vec<f64>, Vec<Complex64>)Expand description
Pre-compute ADMM spectral operators (dipole kernel, inverse operator, and RHS).
For TV-ADMM (QSM.jl’s tv): both are the kernels QSM.jl’s real-to-complex FFT implies
([crate::fft::c2r_kernel]). Returns (fft_workspace, inv_a, f_hat).